Metal-clad polymer article

ABSTRACT

Metal-clad polymer articles containing structural fine-grained and/or amorphous metallic coatings/layers optionally containing solid particulates dispersed therein, are disclosed. The fine-grained and/or amorphous metallic coatings are particularly suited for strong and lightweight articles, precision molds, sporting goods, automotive parts and components exposed to thermal cycling although the CLTE of the metallic layer and the one of the substrate is mismatched. The interface between the metallic layer and the polymer is suitably pretreated to withstand thermal cycling without failure.

FIELD OF THE INVENTION

This invention relates to metal-clad polymer articles comprisingpolymeric materials having a coefficient of linear thermal expansionexceeding 25×10⁻⁶ K⁻¹ in at least one direction and fine-grained(average grain-size: 2-5,000 nm) or amorphous metallic materials havinga coefficient of thermal expansion below 25×10⁻⁶ K⁻¹ enabled by theenhancement of the pull-off strength between the metallic material andthe polymer. The metal-clad polymer articles with mismatchedcoefficients of thermal expansion display good adhesion between themetallic layers and the polymeric materials as well as excellent thermalcycling performance and are suitable for structural applications.

BACKGROUND OF THE INVENTION

The invention relates to metal-clad polymer articles comprisingamorphous or fine-grained metallic coatings/layers on polymericcomposite materials/substrates with good adhesion and thermal cyclingperformance for use in structural applications.

Due to their low cost and ease of processing/shaping by various means,polymeric materials, which are optionally filled with, or reinforcedwith, materials selected from the group of metals, metal alloys, and/orcarbon based materials selected from the group of graphite, graphitefibers, carbon, carbon fibers and carbon nanotubes, glass, glass fibersand other inorganic fillers, are widely used.

Applying metallic coatings or layers to the surfaces of polymer parts orvice versa is of considerable commercial importance because of thedesirable properties obtained by combining polymers and metals. Metallicmaterials, layers and/or coatings are strong, hard, tough and aestheticand can be applied to polymer substrates by various low temperaturecommercial process methods including electroless deposition techniquesand/or electrodeposition. The metal deposits must adhere well to theunderlying polymer substrate even in corrosive environments and whensubjected to thermal cycling and loads, as encountered in outdoor orindustrial service.

The prior art describes numerous processes for metalizing polymers torender them suitable for metal deposition by conditioning thesubstrate's surface to ensure metal deposits adequately bond theretoresulting in durable and adherent metal coatings. The most popularsubstrate conditioning/activation process is chemical etching.

Stevenson in U.S. Pat. No. 4,552,626 (1985) describes a process formetal plating to filled thermoplastic resins such as Nylon-6®. Thefilled resin surface to be plated is cleaned and rendered hydrophilicand preferably deglazed by a suitable solvent or acid. At least aportion of the filler in the surface is removed, preferably by asuitable acid. Thereafter electroless plating is applied to provide anelectrically conductive metal deposit followed by applying at least onemetallic layer by electroplating to provide a desired wear resistantand/or decorative metallic surface. Stevensen provides no information onthermal cycling performance or adhesion strength.

Leech in U.S. Pat. No. 4,054,693 (1977) discloses processes for theactivation of resinous materials with a composition comprising water,permanganate ion and manganate ion at a pH in the range of 11 to 13exhibiting superior peel strengths following electroless metaldeposition. Leech provides no information on thermal cyclingperformance, and adhesion strength is exclusively measured using a peeltest.

Yates in U.S. Pat. No. 5,863,410 (1999) describes an electrolyticprocess for producing copper foil having a matte surface with micropeakswith a height not greater than about 200 microinches (˜5 micron)exhibiting a high peel strength when bonded to a polymeric substrate.

Various patents address the fabrication of articles for a variety ofapplications:

Erb in U.S. Pat. No. 5,352,266 (1994), and U.S. Pat. No. 5,433,797(1995), assigned to the same applicant, describe a process for producingnanocrystalline materials, particularly nanocrystalline nickel. Thenanocrystalline material is electrodeposited onto the cathode in anaqueous acidic electrolytic cell by application of a pulsed current.

Palumbo in U.S. Patent Publication No. 2005/0205425 A1 (2002) and DE10,288,323 (2005), assigned to the same applicant, discloses a processfor forming coatings or freestanding deposits of nanocrystalline metals,metal alloys or metal matrix composites. The process employs tankplating, drum plating or selective plating processes using aqueouselectrolytes and optionally a non-stationary anode or cathode.Nanocrystalline metal matrix composites are disclosed as well.

Tomantschger in U.S. Ser. No. 12/003,224 (2007), assigned to the sameapplicant, discloses variable property deposits of fine-grained andamorphous metallic materials, optionally containing solid particulates.

Palumbo in U.S. Pat. No. 7,320,832 (2008), assigned to the sameapplicant, discloses means for matching the coefficient of thermalexpansion (CTE) of fine-grained metallic coating to the one of thesubstrate by adjusting the composition of the alloy and/or by varyingthe chemistry and volume fraction of particulates embedded in thecoating. The fine-grained metallic coatings are particularly suited forstrong and lightweight articles, precision molds, sporting goods,automotive parts and components exposed to thermal cycling and includepolymeric substrates. Maintaining low CTEs (<25×10⁻⁶ K⁻¹) and matchingthe CTEs of the fine-grained metallic coating with the CTEs of thesubstrate minimizes dimensional changes during thermal cycling andpreventing delamination. Palumbo provides no information on the adhesionstrength.

Palumbo in U.S. Pat. No. 7,354,354 (2008), assigned to the sameapplicant, discloses lightweight articles comprising a polymericmaterial at least partially coated with a fine-grained metallicmaterial. The fine-grained metallic material has an average grain sizeof 2 nm to 5,000 nm, a thickness between 25 micron and 5 cm, and ahardness between 200 VHN and 3,000 VHN. The lightweight articles arestrong and ductile and exhibit high coefficients of restitution and ahigh stiffness and are particularly suitable for a variety ofapplications including aerospace and automotive parts, sporting goods,and the like. Palumbo provides no information on thermal cyclingperformance or adhesion strength.

SUMMARY OF THE INVENTION

It is an objective of the present invention to provide strong,lightweight metal-clad polymer articles for use in structuralapplications, e.g., in automotive, aerospace and defense applications,industrial components, electronic equipment or appliances and sportinggoods, molding applications and medical applications having a metalliclayer applied to a polymeric substrate with enhanced adhesion, pull-offstrength, peel strength, shear strength and thermal cycling performance.

It is an objective of the invention to provide a metallic coating/layerselected from the group of amorphous, fine-grained and coarse-grainedmetal, metal alloy or metal matrix composites. The metalliccoating/layer is applied to the polymer substrate by a suitable metaldeposition process. Preferred metal deposition processes include lowtemperature processes, i.e., processes operating below the softeningand/or melting temperature of the polymer substrates, selected from thegroup of electroless deposition, electrodeposition, physical vapordeposition (PVD), chemical vapor deposition (CVD) and gas condensation.Alternatively, the polymer can be applied to a metallic layer. Themetallic material represents between 5 and 95% of the total weight ofthe article.

It is an objective of the present invention to provide single ormultiple structural metallic layers having a microstructure selectedfrom the group of fine-grained, amorphous, graded and layeredstructures, which have a total thickness in the range of between 10micron and 5 cm, preferably between 25 micron and 2.5 cm and morepreferably between 50 micron and 500 micron.

It is an objective of the invention to provide a metal-clad polymerarticle comprising a shaped or molded polymer component comprisingpolymeric resins or polymeric composites including, but not limited to,epoxies, ABS, polypropylene, polyethylene, polystyrene, vinyls,acrylics, polyamide and polycarbonates. Suitable fillers include carbon,ceramics, oxides, carbides, nitrides, polyethylene, fiberglass and glassin suitable forms including fibers and powders. The polymeric substratehas a room temperature coefficient of linear thermal expansion (CLTE) inat least one direction of between 30×10⁻⁶ K⁻¹ and 500×10⁻⁶ K⁻¹, e.g., ofbetween 30×10⁻⁶ K⁻¹ and 250×10⁻⁶ K⁻¹.

It is an objective of this invention to provide a fine-grained and/oramorphous metallic layer having a room temperature CLTE in alldirections of less than 25×10⁻⁶ K⁻¹, for example, in the range between−5.0×10⁻⁶ K⁻¹ and 25×10⁻⁶ K⁻¹. The metallic layer comprises one or moreelements selected from the group of Ag, Al, Au, Co, Cr, Cu, Fe, Ni, Mo,Pb, Pd, Pt, Rh, Ru, Sn, Ti, W, Zn and Zr. Metal matrix compositesconsist of fine-grained and/or amorphous pure metals or alloys withsuitable particulate additives. The latter additives include powders,fibers, nanotubes, flakes, metal powders, metal alloy powders and metaloxide powders of Al, Co, Cu, In, Mg, Ni, Si, Sn, V, and Zn; nitrides ofAl, B and Si; C (graphite, diamond, nanotubes, Buckminster Fullerenes);carbides of B, Cr, Bi, Si, W; and self lubricating materials such asMoS₂ or organic materials e.g. PTFE. The fine-grained and/or amorphousmetallic material has a high yield strength (300 MPa to 2,750 MPa) andductility (1-15%).

It is an objective of the invention to utilize the enhanced mechanicalstrength and wear properties of fine-grained metallic coatings/layerswith an average grain size between 1 and 5,000 nm, e.g., between 2 and500 nm, and/or amorphous coatings/layers and/or metal matrix compositecoatings exhibiting a coefficient of linear thermal expansion (CLTE) inthe range of 5×10⁻⁶ K⁻¹ to 25×10⁻⁶ K⁻¹ at room temperature in alldirections. Metal matrix composites (MMCs) in this context are definedas particulate matter embedded in a fine-grained and/or amorphous metalmatrix. MMCs can be produced e.g. in the case of using an electrolessplating or electroplating process by suspending particles in a suitableplating bath and incorporating particulate matter into the deposit byinclusion or, e.g., in the case of cold spraying, by addingnon-deformable particulates to the powder feed.

It is another objective of the invention to provide laminate articles,e.g., a metal-clad polymer article, comprising (i) a polymeric materialwhich at room temperature has a coefficient of linear thermal expansionin the range between 30×10⁻⁶ K⁻¹ and 250×10⁻⁶ K⁻¹ in at least onedirection and (ii) a metallic material having a microstructure which isfine-grained with an average grain size between 2 and 5,000 nm and/or anamorphous microstructure, the metallic material being in the form of ametallic layer having a thickness between 10 microns and 2.5 cm and acoefficient of linear thermal expansion in all directions in the rangebetween −5.0×10⁻⁶ K⁻¹ and 25×10⁻⁶ K⁻¹, the coefficient of linear thermalexpansion in all directions of (ii) being at least 20% less than thecoefficient of linear thermal expansion in at least one direction of(i), the laminate article and metal-clad polymer article exhibiting nodelamination and the displacement of said metallic material relative tothe polymeric material or relative to any intermediate layer being lessthan 2% after said articles has been exposed to at least one temperaturecycle according to ASTM B553-71 service condition 1, 2, 3 or 4 andexhibiting a pull-off strength between the polymeric material and themetallic material or between any intermediate layer(s) and the metallicmaterial exceeding 200 psi as determined by ASTM D4541-02 method A-E.

It is another objective of the invention to pretreat the surface ofpolymeric and/or the metallic material to achieve excellent adhesionbetween metallic layer and the polymer material.

It is an objective of the invention to suitably roughen or texture atleast one of the surfaces to be mated to form specific surfacemorphologies, termed “anchoring structures” or “anchoring sites”. Theelimination of smooth surfaces provides for additional surface area foradhesion, increases the bond strength and reduces the risk ofdelamination and/or blistering.

It is an objective of the invention to provide a polymer metal interfaceby creating suitable anchoring structures prior to applying the metal tothe polymer or vice versa. The population of anchoring sites such asrecesses/protrusions and the like enhances the physical bond between thepolymer and the metal. It is an objective to create anchoring structuresat the interface between the polymer and the metal exceeding 10 per cm,preferably exceeding 100 per cm and more preferably exceeding 1,000 percm and up to 100,000 per cm, preferably up to 1,000,000 per cm and morepreferably up to 10,000,000 per cm. Suitable anchoring structures havean average depth and average diameter/width in the range of between 0.01and 5,000 micron. The overall strength of the metal-clad polymer articleis governed by the bond strength between the polymer substrate and theimmediately adjacent metallic layer.

It is another objective of the invention to provide laminate articlesfor components exposed to temperature cycling during use therebyincreasing the need for acceptable CLTE mismatch between polymer and themetallic materials.

It is an objective of the invention to provide a polymeric or metallicsubstrate with an interface layer having a surface roughness Ra in therange of between 0.01 μm and 500 μm and/or Ry (Ry_(max) according toDIN) in the range of 0.01 μm and 5,000 μm. In the context of thisapplication the average surface roughness Ra is defined as thearithmetic means of the absolute values of the profile deviations fromthe mean line and Ry (Ry_(max) according to DIN) is defined as thedistance between the highest peak and the lowest valley of the interfacesurface.

It is an objective of the invention to apply a fine-grained and/oramorphous metallic coating to at least a portion of the surface of apart made substantially of polymer(s) and/or glass fiber compositesand/or carbon/graphite fiber composites including carbon fiber/epoxycomposites, optionally after metallizing the surface (layer thickness≦5micron, preferably ≦1 micron) with a thin layer of nickel, copper,silver or the like for the purpose of enhancing the electricalconductivity of the substrate surface. The fine-grained and/or amorphouscoating is always substantially thicker (≧10 micron) than themetallizing layer. Any metalizing intermediate layer has a coefficientof linear thermal expansion (CLTE) in the range of −5.0×10⁻⁶ K⁻¹ to25×10⁻⁶ K⁻¹ at room temperature in all directions.

According to this invention patches or sleeves which are not necessarilyuniform in thickness can be employed in order to, e.g., enable ametallic thicker coating on selected sections or areas of articlesparticularly prone to heavy use such as in the case of selectedaerospace and automotive components, sporting goods, consumer products,electronic devices and the like.

It is an objective of the invention to achieve adhesion strength asmeasured using ASTM D4541-02 Method A-E “Standard Test Method forPull-Off Strength of Coatings Using Portable Adhesion Testers” betweenthe metallic material/coating and the polymer material/substrate whichexceeds 200 psi, preferably 300 psi, preferably 500 psi and morepreferably 600 psi and up to 6,000 psi.

It is an objective of the invention to suitably precondition the polymersubstrate surface to enhance the adhesion between the polymer substrateand the metallic layer and achieve a strong interfacial bond between thepolymer and the metal.

It is an objective of the invention to improve the adhesion between thepolymeric substrate and the metallic layer by a suitable heat treatmentof the metal-clad article for between 5 minutes and 50 hours at between50 and 200° C.

It is an objective of this invention to provide articles composed offine-grained and/or amorphous metallic coatings on composite polymericsubstrates capable of withstanding 1, preferably 5, more preferably 10,more preferably 20 and even more preferably 30 temperature cycleswithout failure according to ANSI/ASTM specification B604-75 section 5.4(Standard Recommended Practice for Thermal Cycling Test for Evaluationof Electroplated Plastics ASTM B553-71) for service condition 1,preferably service condition 2, preferably service condition 3 and evenmore preferably for service condition 4.

It is an objective of this invention to provide lightweightpolymer/metal-hybrid articles with increased strength, stiffness,durability, wear resistance, thermal conductivity and thermal cyclingcapability.

It is an objective of this invention to provide polymer articles, coatedwith fine-grained and/or amorphous metallic layers that are stiff,lightweight, resistant to abrasion, resistant to permanent deformation,do not splinter when cracked or broken and are able to withstand thermalcycling without degradation, for a variety of applications including,but not limited to: (i) applications requiring cylindrical objectsincluding gun barrels; shafts, tubes, pipes and rods; golf and arrowshafts; skiing and hiking poles; various drive shafts; fishing poles;baseball bats, bicycle frames, ammunition casings, wires and cables andother cylindrical or tubular structures for use in commercial goods;(ii) medical equipment including orthopedic prosthesis and surgicaltools crutches, wheel chairs and medical equipment including orthopedicprosthesis, implants and surgical tools; (iii) sporting goods includinggolf shafts, heads and faceplates; lacrosse sticks; hockey sticks; skisand snowboards as well as their components including bindings; racquetsfor tennis, squash, badminton; bicycle parts; (iv) components andhousings for electronic equipment including laptops; TVs and handhelddevices including cell phones; personal digital assistants (PDAs)devices; walkmen; discmen; MP3 players and Blackberry®-type devices;cameras and other image recording devices as well as TVs; (v) automotivecomponents including heat shields; cabin components including seatparts, steering wheel and armature parts; fluid conduits including airducts, fuel rails, turbocharger components, oil, transmission and brakeparts, fluid tanks and housings including oil and transmission pans;cylinder head covers; spoilers; grill-guards and running boards; brake,transmission, clutch, steering and suspension parts; brackets andpedals; muffler components; wheels; brackets; vehicle frames; spoilers;fluid pumps such as fuel, coolant, oil and transmission pumps and theircomponents; housing and tank components such as oil, transmission orother fluid pans including gas tanks; electrical and engine covers; (vi)industrial/consumer products and parts including linings on hydraulicactuator, cylinders and the like; drills; files; knives; saws; blades;sharpening devices and other cutting, polishing and grinding tools;housings; frames; hinges; sputtering targets; antennas as well aselectromagnetic interference (EMI) shields; (vii) molds and moldingtools and equipment; (viii) aerospace parts and components includingwings; wing parts including flaps and access covers; structural sparsand ribs; propellers; rotors; rotor blades; rudders; covers; housings;fuselage parts; nose cones; landing gear; lightweight cabin parts;cryogenic storage tanks; ducts and interior panels; wings, rotors,propellers and their components and (ix) military products includingammunition, armor as well as firearm components, and the like; that arecoated with fine-grained and/or amorphous metallic layers that arestiff, lightweight, resistant to abrasion, resistant to permanentdeformation, do not splinter when cracked or broken and are able towithstand thermal cycling without degradation.

It is an objective of this invention to at least partially coat theinner or outer surface of parts including complex shapes withfine-grained and/or amorphous metallic materials that are strong,lightweight, have high stiffness (e.g. resistance to deflection andhigher natural frequencies of vibration) and are able to withstandthermal cycling without degradation.

Accordingly, the invention in one embodiment denoted the firstembodiment, is directed to a metal-clad polymer article comprising:

-   -   (i) a polymeric material which at room temperature has a        coefficient of linear thermal expansion in the range between        30×10⁻⁶ K⁻¹ and 250×10⁻⁶ K⁻¹ in at least one direction; and    -   (ii) a metallic material having a microstructure which is        fine-grained with an average grain size between 2 and 5,000 nm        and/or an amorphous microstructure, the metallic material being        in the form of a metallic layer having a thickness between 10        micron and 2.5 cm and a coefficient of linear thermal expansion        in all directions in the range between −5.0×10⁻⁶ K⁻¹ and 25×10⁻⁶        K⁻¹;    -   (iii) with or without at least one intermediate layer between        the polymeric material and the metallic material (having a        coefficient of linear thermal expansion in all directions in the        range between −5.0×10⁻⁶ K⁻¹ and 250×10⁻⁶ K⁻¹;    -   (iv) an interface between the polymeric material and the        metallic material or an interface between the polymeric material        and any intermediate layer(s) and an interface between any        intermediate layer(s) and the metallic material;    -   (v) anchoring structure at said interface(s) comprising recesses        and/or protrusions to increase the interface area and provide        enhanced physical bond at the interface between the polymeric        material and the metallic material or at the interface between        the polymeric material and any intermediate layer;    -   (vi) said metal-clad polymer article exhibiting no delamination        and the displacement of said metallic material of (ii) relative        to the polymeric material of (i) or relative to any intermediate        layer(s) being less than 2% after said article has been exposed        to at least one temperature cycle according to ASTM B553-71        service condition 1, 2, 3 or 4; and    -   (vii) said metal-clad polymer article exhibiting a pull-off        strength between the polymeric material of (i) and the metallic        material of (ii) or any intermediate layer exceeding 200 psi as        determined by ASTM D4541-02 Method A-E; and    -   (viii) said metal-clad polymer article or portion thereof having        a yield strength and/or ultimate tensile strength of between 10        and 7,500 MPa and an elastic limit between 0.5 and 30%.

Accordingly, the invention in another embodiment, denoted secondembodiment, is directed to a metal-clad polymer article comprising:

-   -   (i) a polymeric material which at room temperature has a        coefficient of linear thermal expansion in the range between        30×10⁻⁶ K⁻¹ and 250×10⁻⁶ K⁻¹, in at least one direction;    -   (ii) a metallic material having a microstructure which is        fine-grained with an average grain size between 2 and 5,000 nm        and/or an amorphous microstructure, the metallic material being        in the form of a metallic layer having a thickness between 10        micron and 2.5 cm and a coefficient of linear thermal expansion        in all directions in the range between −5.0×10⁻⁶ K⁻¹ and 25×10⁻⁶        K⁻¹, the coefficient of linear thermal expansion in all        directions being at least 20% less than the coefficient of        linear thermal expansion in at least one direction of (i);    -   (iii) with or without at least one intermediate layer between        the polymeric material and the metallic material having a        coefficient of linear thermal expansion in all directions in the        range between −5.0×10⁻⁶ K⁻¹ and 250×10⁻⁶ K⁻¹, the coefficient of        linear thermal expansion in all directions of (ii) being at        least 20% less than the coefficient of linear thermal expansion        in at least one direction of (i);    -   (iv) an interface between the polymeric material and the        metallic material or an interface between the polymeric material        and any intermediate layer(s) and an interface between any        intermediate layer(s) and the metallic material;    -   (v) anchoring structure at said interface(s) comprising recesses        and/or protrusions to increase the interface area and provide        enhanced physical bond at the interface between the polymeric        material and the metallic material or at the interface between        the polymeric material and any intermediate layer;    -   (vi) said metal-clad polymer article exhibiting no delamination        and the displacement of said metallic material of (ii) relative        to the polymeric material of (i) being less than 2% after said        article has been exposed to at least one temperature cycle        according to ASTM B553-71 service condition 1, 2, 3 or 4; and    -   (vii) said metal-clad polymer article exhibiting a pull-off        strength between the polymeric material of (i) and the metallic        material of (ii) or any intermediate layer exceeding 200 psi as        determined by ASTM D4541-02 Method A-E; and    -   (viii) said metal-clad polymer article or portion thereof having        a yield strength and/or ultimate tensile strength of between 10        and 7,500 MPa and an elastic limit between 0.5 and 30%.

Accordingly the invention in still another embodiment it denoted thethird embodiment is directed to a method for preparing the metal-cladpolymer article of the first embodiment comprising:

-   -   (i) providing a polymeric material which at room temperature has        a coefficient of linear thermal expansion exceeding 30×10⁻⁶ K⁻¹        in at least one direction.    -   (ii) providing a metallic material having a microstructure which        is fine-grained with an average grain size between 2 and 5,000        nm and/or an amorphous microstructure where the metallic        material is in the form of a metallic layer having a thickness        between 10 microns and 2.5 cm and a coefficient of linear        thermal expansion in all directions in the range between        −5.0×10⁻⁶ K⁻¹ and 25×10⁻⁶ K⁻¹,    -   (iii) optionally providing at least one electrically conductive        or electrically nonconductive adhesive intermediate layer,    -   (iv) providing interface(s) between the polymeric material and        the metallic layer and between the polymeric material and any        intermediate layer and between any intermediate layer and the        metallic layer and between any adjacent intermediate layers,    -   (v) providing anchoring structure at said interfaces to anchor        polymeric material to metallic layer or polymeric material to        any intermediate layer, and metallic layer to any intermediate        layer or in the case of intermediate layers to anchor one        intermediate layer to another.

In one aspect of the third embodiment the coefficient of linear thermalexpansion in all directions of the metallic layer and of anyintermediate layer(s) is at least 20% less than the coefficient oflinear thermal expansion in at least one direction of the polymericmaterial. In one case of the third embodiment a metallic layer isdeposited onto a polymeric substrate having anchoring structureassociated therewith by electrodeposition, physical vapor deposition(PVD), and chemical vapor deposition (CVD). In another case of the thirdembodiment the polymeric material is applied to the metallic layerhaving anchoring structure associated therewith.

As used herein, the terms “laminate article” and “metal-clad article”means an item which contains at least one polymeric layer and at leastone metallic layer in contact with each other.

As used herein, the term “coating” means deposit layer applied to partor all an exposed surface of a substrate.

As used herein, the term “coating thickness” or “layer thickness” refersto so depth in a deposit direction.

As used herein, “anodically assisted chemical etching” means that thesurface of a polymeric substrate to be coated is activated by applyinganodic polarization to the substrate which is submersed in a chemicaletching solution thereby simultaneously chemically and electrochemicallyactivating the surface to achieve a superior bond between the substrateand the subsequently applied coating.

As used herein, the term “anchoring structures” refers to surfacefeatures including recesses/protrusions purposely created in theinterface between the polymeric material and the metallic material layeror the interface between the polymeric material and the intermediatelayer, e.g., in the polymeric material or in the metallic material layeror in any intermediate layer, to enhance their bond strength.

As used herein, the term “population of anchoring structures” refers tonumber of surface features per unit length or area. The “linearpopulation of anchoring structures” can be obtained by counting thenumber of features, e.g. on a cross sectional image and normalizing itper unit length, e.g., per cm. The average “areal population ofanchoring structures” is the square of the average linear population,e.g., expressed in cm² or mm². Alternatively, the average areal densitycan be obtained by counting the number of features visible in an opticalmicrograph, SEM image or the like and normalizing the count for themeasurement area.

As used herein, “surface roughness”, “surface texture” and “surfacetopography” mean an irregular surface topography such as a polymermaterial or metallic material layer or intermediate layer surfacecontaining anchoring structures. Surface roughness consists of surfaceirregularities which result from the various surface preconditioningmethods used such as mechanical abrasion and etching to create suitableanchoring structures. These surface irregularities/anchoring structurescombine to form the “surface texture” which directly influences the bondstrength achieved between the polymeric article and the metallic layer.

In practice there are many different parameters used for analyzingsurface finish, and many more have been developed for specialproducts/circumstances. The parameter most frequently used in NorthAmerica for surface roughness is Ra. It measures the average roughnessby comparing all the peaks and valleys to the mean line, and thenaveraging them all over the entire length that a stylus is draggedacross the surface. It's also referred to as CLA (center line average)and AA (area average). Benefits of using the Ra method are itssimplicity and its widespread use. The RMS (root mean square) of a givensurface typically runs about 10% higher than its equivalent Ra (averageroughness) value.

In reality, however, the Ra value neither provides a detailed enoughdescription of a surface finish of a part nor an absolute indication ofthe achievable adhesion strength when bonded to another material.Another parameter that can be useful is Ry_(max) formerly called justR_(max). This is an ISO standard that measures the distance between thehighest peak and the lowest valley over a cutoff length. This is,however, a sensitive method and, if over the measurement length ascratch or imperfection is encountered, the reading may be meaningless.Similarly, Ry depicts the maximum roughness depth.

Another parameter most widely used in Europe is Rz, or mean roughnessdepth. The Rz ISO standard is also called “Ten Point Average Roughness”.It averages the height of the five highest peaks and the depth of thefive lowest valleys over the measuring length, using an unfilteredprofile. The Rz DIN standard averages the highest point and lowest pointover five cutoffs.

As used herein, the term “intermediate layer” means a layer locatedbetween and in intimate contact with a polymeric material substrate anda metallic layer or another intermediate layer. Examples of intermediatelayers include “intermediate conductive layers” or “metalizing layers”applied to the surface of the polymer material to enhance the surface toenable electroplating. The intermediate layer can comprise a metalliclayer, an oxide layer, a polymeric material layer such as an adhesivelayer, or a polymer layer with conductive particulates embedded therein.

As used herein, the term “molding” of polymers means shaping of anarticle to its near final shape using injection molding, blow molding,compression molding, transfer molding, rotational molding, extrusion,thermoforming, vacuum forming or other suitable shaping methodsavailable for polymers.

As used herein “delamination” means failure of a laminated structure bythe separation between two layers comprised of different chemicalcompositions resulting in the physical splitting of the layers.

As used herein “displacement” means the difference between a laterposition of a coating and its original position on a substrate caused bythe relative movement of a coating, e.g., induced by thermal cycling oflaminates composed of layers with different CLTEs.

According to one aspect of the present invention an article is providedby a process which comprises the steps of, positioning the metallic ormetallized work piece to be plated in a plating tank containing asuitable electrolyte and a fluid circulation system, providingelectrical connections to the work piece/cathode to be plated and to oneor several anodes and plating a structural layer of a metallic materialwith an average grain size of equal to or less than 5,000 nm on thesurface of the metallic or metallized work piece using suitable directcurrent (D.C.) or pulse electrodeposition processes described, e.g., inthe copending application US Patent Publication No. US2005-020542A1,published Sep. 22, 2005 (DE 10,288,323; 2005).

Metal-clad polymer articles of the invention comprise fine-grainedand/or amorphous metallic layers having low CLTEs e.g. −5.0×10⁻⁶ K⁻¹ to25×10⁻⁶ K⁻¹ in all directions, having a layer thickness of at least0.010 mm, preferably more than 0.020 mm, more preferably more than 0.030mm and even more preferably more that 0.050 mm on polymeric substrateshaving CLTEs in at least one direction of between 30×10⁻⁶ K⁻¹ to500×10⁻⁶ K⁻¹.

Articles of the invention comprise a single or several fine-grainedand/or amorphous metallic layers applied to the substrate as well asmulti-layer laminates composed of alternating layers of fine-grainedand/or amorphous metallic layers and polymeric substrates.

The fine-grained metallic coatings/layers have a grain size under 5 μm(5,000 nm), preferably in the range of 5 to 1,000 nm, more preferablybetween 10 and 500 nm. The grain size can be uniform throughout thedeposit; alternatively, it can consist of layers with differentmicrostructure/grain size. Amorphous microstructures and mixedamorphous/fine-grained microstructures are within the scope of theinvention as well.

According to this invention, the entire polymer surface can be coated;alternatively, metal patches or sections can be formed on selected areasonly (e.g. golf club face plates or sections of golf club shafts, arrowsor polymer cartridge casings), without the need to coat the entirearticle.

According to this invention metal patches or sleeves which are notnecessarily uniform in thickness and/or microstructure can be depositedin order to e.g. enable a thicker coating on selected sections orsections particularly prone to heavy use such as golf club face or soleplates, the tip end of fishing poles, arrows and shafts for golf clubs,skiing or hiking poles, polymer cartridge casings, automotive componentsand the like.

According to this invention laminate articles in one aspect comprisefine-grained and/or amorphous metal layers on carbon-fiber and/or glassfiber filled polymeric substrates.

The following listing further defines the laminate article/metal-cladarticle of the invention:

Polymeric Substrate Specification:

-   Minimum coefficient of linear thermal expansion in at least one    dimension [10⁻⁶ K⁻¹]: 25; 30, 50-   Maximum coefficient of linear thermal expansion in at least one    dimension [10⁻⁶ K⁻¹]: 250; 500-   Polymeric materials comprise at least one of: unfilled or filled    epoxy, phenolic or melamine resins, polyester resins, urea resins;    thermoplastic polymers such as thermoplastic polyolefins (TPOs)    including polyethylene (PE) and polypropylene (PP); polyamides,    mineral filled polyamide resin composites; polyphthalamides,    polyphtalates, polystyrene, polysulfone, polyimides; neoprenes;    polybutadienes; polyisoprenes; butadiene-styrene copolymers;    poly-ether-ether-ketone (PEEK); polycarbonates; polyesters; liquid    crystal polymers such as partially crystalline aromatic polyesters    based on p-hydroxybenzoic acid and related monomers; polycarbonates;    acrylonitrile-butadiene-styrene (ABS); chlorinated polymers such    polyvinyl chloride (PVC); and fluorinated polymers such as    polytetrafluoroethylene (PTFE). Polymers can be crystalline,    semi-crystalline or amorphous.-   Filler additions: metals (Ag, Al, In, Mg, Si, Sn, Pt, Ti, V, W, Zn);    metal oxides (Ag₂O, Al₂O₃, SiO₂, SnO₂, TiO₂, ZnO); carbides of B,    Cr, Bi, Si, W; carbon (carbon, carbon fibers, carbon nanotubes,    diamond, graphite, graphite fibers); glass; glass fibers; fiberglass    metallized fibers such as metal coated glass fibers; mineral/ceramic    fillers such as talc, calcium silicate, silica, calcium carbonate,    alumina, titanium dioxide, ferrite, mica and mixed silicates (e.g.    bentonite or pumice).-   Minimum particulate/fiber fraction [% by volume]: 0; 1; 5; 10-   Maximum particulate/fiber fraction [% by volume]: 50; 75; 95    Metallic Coating/Metallic Layer Specification:-   Minimum coefficient of linear thermal expansion [10⁻⁶ K⁻¹]: −5.0;    −1.0; 0-   Maximum coefficient of linear thermal expansion [10⁻⁶ K⁻¹]: 15; 20;    25-   Microstructure: Amorphous or crystalline-   Minimum average grain size [nm]: 2; 5; 10-   Maximum average grain size [nm]: 100; 500; 1,000; 5,000; 10,000-   Metallic layer Thickness Minimum [μm]: 10; 25; 30; 50; 100-   Metallic layer Thickness Maximum [mm]: 5; 25; 50-   Metallic materials comprising at least one of: Ag, Al, Au, Co, Cr,    Cu, Fe, Ni, Mo, Pb, Pd, Pt, Rh, Ru, Sn, Ti, W, Zn and Zr-   Other alloying additions: B, C, H, O, P and S-   Particulate additions: metals (Ag, Al, In, Mg, Si, Sn, Pt, Ti, V, W,    Zn); metal oxides (Ag₂O, Al₂O₃, SiO₂, SnO₂, TiO₂, ZnO); carbides of    B, Cr, Bi, Si, W; carbon (carbon nanotubes, diamond, graphite,    graphite fibers); glass; polymer materials (PTFE, PVC, PE, PP, ABS,    epoxy resins)-   Minimum particulate fraction [% by volume]: 0; 1; 5; 10-   Maximum particulate fraction [% by volume]: 50; 75; 95-   Minimum Yield Strength Range [MPa]: 300-   Maximum Yield Strength Range [MPa]: 2,750-   Minimum Hardness [VHN]: 100; 200; 400-   Maximum Hardness [VHN]: 800; 1,000; 2,000-   Minimum Deposition Rates [mm/hr]: 0.01; 0.05; 0.1; 0.2; 0.5    Intermediate Layer Specification:-   Metallic Layer: composition selected from metallic materials list    set forth above, including electroless Ni, Cu, Co and/or Ag    comprising coatings; metallic layers can contain an oxide layer on    the outer surface, which can promote the bond strength to the    polymer substrate.-   Oxide layer: oxides of elements as listed in the metallic materials    list, including Ni, Cu, Ag oxides-   Polymeric Layer: composition selected from polymeric materials list    including partly cured layers prior to coating and finishing heat    treatment, also cured polymeric paint (carbon, graphite, Cu, Ag    filled curable polymers, adhesive layer.-   Intermediate Layer Thickness Minimum [μm]: 0.005; 0.025;-   Intermediate Layer Thickness Maximum [μm]: 1; 5; 25; 50    Interface Specification (Polymer/Intermediate Layer Interface or    Polymer/Metallic Layer Interface):-   Minimum surface roughness Ra, Ry, Ry_(max), Rz [μm]: 0.01; 0.02;    0.05; 0.1; 1-   Maximum surface roughness Ra, Ry, Ry_(max), Rz [μm]: 25; 50; 500;    5,000-   Minimum linear population of anchoring surface structures [number    per cm]: 10; 100; 1,000-   Maximum linear population of anchoring surface structures [number    per cm]: 10⁵; 10⁶; 10⁷-   Minimum areal population of anchoring surface structures [number per    mm²]: 1, 100; 10⁴-   Maximum areal population of anchoring surface structures [number per    mm²]: 10⁷; 10¹⁰-   Minimum anchoring structure diameter [nm]: 10, 50, 100-   Maximum anchoring structure diameter [μm]: 500; 1,000-   Minimum anchoring structure height/depth [nm]: 10, 50, 100-   Maximum anchoring structure height/depth [μm]: 500; 1,000-   Anchoring surface structure topography: recesses; protrusions;    “inkbottle type” cavities; pitted anchoring surface structures;    holes; pores; depressions; anchoring surfaces with protruding    anchoring fibers; grooved, roughened and etched anchoring surface    structures; nodules; dimples; mounds; as well as honeycomb or open    foam type structures; “brain”, “cauliflower”, “worm”, “coral” and    other three dimensionally interconnected porous surface structures.    Typically any number of different anchoring structures is present in    the suitably textured surface, their shapes and areal densities can    be irregular and the clear identification of individual anchoring    structures can be subject to interpretation. The most reliable    method therefore to account for the effect of anchoring structures    is to measure the adhesion property of the metal-clad polymer    article, e.g., using the ASTM D4541-02 pull-off strength test.    Metal-Clad Polymer Article Specification:    Adhesion:-   Minimum pull-off strength of the coating according to ASTM D4541-02    Method A-E [psi]: 200; 300; 400; 600-   Maximum pull-off strength of the coating according to ASTM D4541-02    Method A-E [psi]: 2,500; 3,000; 6,000    Thermal Cycling Performance:-   Minimum thermal cycling performance according to ASTM B553-71: 1    cycle according to service condition 1 without failure (no    blistering, delamination or <2% displacement) and with <2%    displacement between the polymer and metallic material layers.-   Maximum thermal cycling performance according to ASTM B553-71:    infinite number of cycles according to service condition 4 without    failure.    Metal-Clad Polymer Article Mechanical Properties:-   Polymer substrate weight fraction of the metal-clad polymer article    [%]: 5 to 95-   Minimum yield strength of the metal-clad polymer article [MPa]: 5;    10; 25; 100-   Maximum yield strength of the metal-clad polymer article [MPa]:    5,000; 7,500.-   Minimum ultimate tensile strength of the metal-clad polymer article    [MPa]: 5; 25; 100-   Maximum ultimate tensile strength of the metal-clad polymer article    [MPa]: 5,000; 7,500-   Minimum elastic limit of the metal-clad polymer article [%]: 0.5; 1-   Maximum elastic limit of the metal-clad polymer article [%]: 5; 10,    30

The following description summarizes the test protocols used:

Adhesion Test Specification:

ASTM D4541-02 “Standard Test Method for Pull-Off Strength of CoatingsUsing Portable Adhesion Testers” is a test for evaluating the pull-offstrength of a coating on rigid substrates determining the greatestperpendicular force (in tension) that a coating/substrate interfacesurface area can bear before it detaches either by cohesive or adhesivefailure. This test method maximizes tensile stress as compared to shearstress applied by other methods, such as scratch or knife adhesion andthe results may not be comparable. ASTM D4541-02 specifies fiveinstrument types identified as test Methods A-E and the pull offstrength reported is an average of at least three individualmeasurements.

Thermal Cycling Test Specification:

ANSI/ASTM specification B604-75 section 5.4 Test (Standard RecommendedPractice for Thermal Cycling Test for Evaluation of ElectroplatedPlastics ASTM B553-71). In this test the samples are subjected to athermal cycle procedure as indicated in Table 1. In each cycle thesample is held at the high temperature for an hour, cooled to roomtemperature and held at room temperature for an hour and subsequentlycooled to the low temperature limit and maintained there for an hour.

TABLE 1 Standard Recommended Practice for Thermal Cycling Test forEvaluation of Electroplated Plastics According to ASTM B553-71 ServiceCondition High Limit [° C.] Low Limit [° C.] 1 (mild) 60 −30 2(moderate) 75 −30 3 (severe) 85 −30 4 (very severe) 85 −40

If any blistering, delamination or cracking is noted the test isimmediately suspended. After 10 such test cycles the sample is allowedto cool to room temperature, is carefully checked for delamination,blistering and cracking and the total displacement of the coatingrelative to the substrate is determined.

DETAILED DESCRIPTION

This invention relates to laminate articles comprising structuralmetallic material layers on polymeric substrates that are suitablyshaped to form a precursor of the metal-clad polymer article. Themetallic materials/coatings are fine-grained and/or amorphous and areproduced by DC or pulse electrodeposition, electroless deposition,physical vapor deposition (PVD), chemical vapor deposition (CVD) and gascondensation or the like. The intrinsic mismatch of the coefficient ofthermal expansion of the metal and the polymer of the inventivemetal-clad polymer articles is overcome and acceptable thermal cyclingperformance achieved by enhancing the pull-off strength between themetallic material and the polymer by suitable surface activation and/orsurface roughness and/or metal-polymer interface surface design.

The person skilled in the art of plating will know how to electroplateor electroless plate selected fine-grained and/or amorphous metals,alloys or metal matrix composites choosing suitable plating bathformulations and plating conditions. Similarly, the person skilled inthe art of PVD, CVD and gas condensation techniques will know how toprepare fine-grained and/or amorphous metal, alloy or metal matrixcomposite coatings.

Applying metallic coatings to polymer and polymer composite parts is inwidespread use in consumer and sporting goods, automotive and aerospaceapplications. Polymer composites with carbon/graphite and/or glassfibers are relatively inexpensive, easy to fabricate and machine;however, they are not very durable. Metallic coatings are thereforefrequently applied to polymers and polymer composites to achieve therequired mechanical strength, wear and erosion resistance and to obtainthe desired durability and service life. To achieve the requireddurability of laminate articles excellent bond strength between themetallic layer and the polymer substrate is of paramount importance.

A variety of fine-grained and/or amorphous metallic coatings, which atroom temperature have a coefficient of thermal expansion in the rangebetween minus 5.0×10⁻⁶ K⁻¹ and 25×10⁻⁶ K⁻¹ in all directions, can beemployed. Particularly suited are fine-grained and/or amorphoushigh-strength pure metals or alloys containing Ag, Al, Au, Co, Cr, Cu,Fe, Ni, Mo, Pb, Pd, Pt, Rh, Ru, Sn, Ti, W, Zn and Zr; and optionally oneor more elements selected from the group consisting of B, C, H, O, P andS; and/or optionally containing particulate additions such as metalpowders, metal alloy powders and metal oxide powders of Ag, Al, Au, Cu,Co, Cr, Fe, Ni, Mo, Pd, Pt, Sn, Rh, Ru, Ti, W, Zn and Zr; nitrides ofAl, B and Si; C (graphite, carbon fibers, carbon nanotubes or diamond);carbides of B, Cr, Bi, Si, W; ceramics, glasses and polymer materialssuch as polytetrafluoroethylene (PTFE), polyvinylchloride (PVC),acrylonitrile-butadiene-styrene (ABS), polyethylene (PE), polypropylene(PP). The particulate average particle size is typically between 500 nmand 5 μm.

Metallic coatings can have a coarse-grained, fine-grained or amorphousmicrostructure. One or more metallic coating layers of a single orseveral chemistries and microstructures can be employed. The metalliccoating can be suitably exposed to a finishing treatment, which caninclude, among others, electroplating, i.e., chromium plating andapplying a polymeric material, i.e., paint or adhesive.

Polymeric substrates, for the most part have a CLTE significantlyexceeding 25×10⁻⁶ K⁻¹ in at least one direction. Selected polymericmaterials and particularly filled or reinforced polymeric materials, candisplay coefficient of thermal expansion values which are not isotropic,but vary significantly with the direction. As an example, glass filledpolyamide can have coefficient of linear thermal expansion (CLTE) valuesas low 20-75×10⁻⁶ K⁻¹ in one direction and as high as 100-250×10⁻⁶ K⁻¹in another direction. In the case of fiber reinforced polymer materials,as fibers usually align in the plane of the part during molding, theCLTE of the polymer in the plane is typically lower than the CLTEperpendicular/normal to it. The degree of CLTE match or CLTE mismatchbetween the coating and the substrate and the bond strength between thecoating and the substrate play an important role in preventingdelamination and affecting the relative coating/substrate displacementin industrial composite parts exposed to thermal cycling. To clarify,the stronger the bond strength between the polymer and the metallicmaterial the more CLTE mismatch and the higher the temperaturefluctuations the metal-clad polymer article can endure. It is thereforeof crucial importance to suitably roughen/pretreat/activate thepolymeric surface to ensure the bond strength to the coatings andparticularly metallic coatings is optimized. Of course, mechanicalproperties of the substrate and coating are important as well,particularly the yield strength, ultimate tensile strength, resilienceand elongation.

Suitable polymeric substrates include unfilled or filled epoxy, phenolicand melamine resins, polyester resins, urea resins; thermoplasticpolymers such as thermoplastic polyolefins (TPOs) including polyethylene(PE) and polypropylene (PP); polyamides, mineral filled polyamide resincomposites; polyphthalamides; polyphtalates, polystyrene, polysulfone,polyimides; neoprenes; polybutadienes; polyisoprenes; butadiene-styrenecopolymers; poly-ether-ether-ketone (PEEK); polycarbonates; polyesters;liquid crystal polymers such as partially crystalline aromaticpolyesters based on p-hydroxybenzoic acid and related monomers;polycarbonates; acrylonitrile-butadiene-styrene (ABS); chlorinatedpolymers such polyvinyl chloride (PVC); and fluorinated polymers such aspolytetrafluoroethylene (PTFE).

These polymeric substrates are frequently reinforced by adding suitablefillers including carbon, carbon nanotubes, graphite, graphite fibers,carbon fibers, metals, metal alloys, glass and glass fibers; fiberglass,metallized fibers such as metal coated glass fibers and the like.Appropriate filler additions in the substrate range from as low as 2.5%per volume or weight to as high as 95% per volume or weight. In additionto fillers with a high aspect ratio, other fillers such as glass,ceramics and mineral fillers such as talc, calcium silicate, silica,calcium carbonate, alumina, titanium dioxide, ferrite, and mixedsilicates (e.g. bentonite or pumice) can be employed as well.

Particularly suitable substrates include carbon/graphite fiber and glassfiber resin composites in which the resin components include phenolicresins, epoxy resins, polyester resins, urea resins, melamine resins,polyimide resins, polyamide resins as well as elastomers such as naturalrubber, polybutadienes, polyisoprenes, butadiene-styrene copolymers,polyurethanes, and thermoplastics such as polyethylene, polypropylene,and the like.

During molding/shaping of the precursor metal-clad article, polymerchains do not necessarily align themselves in a random manner but ratherdisplay directionality depending on part geometry, molding conditions,material flow patterns etc. Similarly, fiber additions usually align inthe plane and the electrical and thermal conductivities of suchcomposites in a plane can be 10-100 times higher than perpendicular tothe plane. Therefore, directional properties need to be considered inmetal-clad polymer articles. Furthermore, non uniformity of the moldedpolymer or polymer matrix composite substrates can at times beexacerbated near the surface and significant differences in compositionand properties near the outer surface layer, which participates informing the bond to a coating layer and the interior bulk of the moldedpolymer, can exist.

To enhance the bond between the metallic layer, i.e., themetallizing/intermediate layer or the fine-grained/amorphous metalliclayer and the polymer, polymeric surfaces forming the interface with themetallic layer are typically preconditioned before the metallic layersare applied. Numerous attempts have been made to identify, characterizeand quantify desired surface features which result in achieving thedesired bonding properties and to quantify the surface topography andsurface roughness in quantifiable scientific terms. Heretofore, theseefforts have not succeeded in part because of the complexity of thesurface features, the numerous parameters such as population, size andshape of the anchoring structures which affect the mechanicalinterlocking. Furthermore, it is not even clear if the bond strengthbetween metals and polymers is entirely dictated by mechanical forces orif chemical interactions, e.g., between functional surface groups of thepolymers present or introduced during etching, contribute to the bondstrengths as typically after etching the wetting angle is reduced due tothe creation of hydrophilic functional groups, i.e., —COOH and —COH.Similarly, the metal surface at the interface can be at least partiallyoxidized which at times can enhance the adhesion.

Anchoring structures are surface features induced on the polymericsurface by the various surface preconditioning methods used including,but not limited to, mechanical abrasion, swelling, dissolution, chemicaletching and plasma etching, and furthermore depend on the composition ofthe polymer substrate and the amount, size and shape of fillersemployed. In practice when dealing with polymeric and metallic surfacesthat are pretreated to improve adhesion, surface features are usuallyquite irregular and difficult to describe/measure in absolute terms andattempts to quantify surface features responsible for good adhesionbetween the coating and the substrate have not been successful to date.Alternatively, as outlined in another preferred embodiment the polymercan be applied to a suitably rough metal substrate.

Over time a variety of standardized tests measuring adhesion have beendeveloped and results from one test are frequently not comparable withresults obtained with another test. The most popular test for adhesionbetween the metallic coating and a polymer substrate are peel tests. Theforce measured to peel a thin coating off the substrate relates to aforce required to propagate debonding and before the test is initiatedthe coating is purposely debonded from the substrate. Peel tests measurethe interfacial fracture energy and are used to characterize adhesiveand thin metal coatings (decorative coatings) up to a thickness of 20microns. When the thickness and the strength of the coatings increase,e.g., in the case of thick structural coatings/layers employingfine-grained metallic coatings, peel tests do not provide meaningfulresults. Pull-off tests, on the other hand, measure the force requiredto debond a unit area of the interface of the substrate and the coatingand, in the case of metal-clad polymer articles with structural metalliclayers, they are more relevant as the objective is to increase the forcerequired for initiation of debonding as much as possible. In contrast topeel tests, pull-off test results are unaffected by the coatingthickness. As illustrated in selected examples below there is noreliable correlation between pull-off and peel strength data.

Ways are sought to enable tolerating a larger CLTE mismatch between ametallic coating/layer and polymeric materials/substrates employed instrong, lightweight and structural laminate/metal-clad polymer articlesas the bond strength achieved remains significantly below the oneachieved between metallic coatings and metallic substrates. As theappropriate surface preparation of the substrate is known to have asignificant impact on the bond strength and adhesion, the preferredapproach is to provide means of substantially enhancing the bondstrength between the metallic layer and the polymer. As highlighted, thesurface topography created during the pretreatment procedure has asignificant effect on adhesion. Ideally, when employing surfacepretreatment methods, anchoring structures selected from the group of“inkbottle type” cavities, pitted anchoring surface structures, nodules,anchoring surfaces with protruding anchoring fibers, grooved, roughenedand etched anchoring surface structures are formed at the interfacebetween the metallic layer and the polymeric substrates and interlockthe metallic and polymer layers raising the adhesion strength. Thenumber, population density, shape, size and depth of anchoringstructures greatly affects the bond strength achievable and thereforestandardized adhesion tests are required to determine and objectivelycompare bond quality such as ASTM D4541-02.

Platable polymeric compositions therefore frequently employ “removablefillers” which are extracted from the near surface of the metal-polymerinterface by a suitable pretreatment prior to metal deposition. In thecase of polymer composites containing “permanent fibers” pretreatmentmethods and conditions can be optimized to “expose” some of the embeddedfibers to enable the coating to adhere thereto and, at least partiallyencapsulate them, again resulting in enhanced bond strength and in anincrease in CLTE mismatch between the coating and the substrate that canbe tolerated. Many suitable polymeric compositions therefore containboth removable and permanent fillers. Leaching of the removable fillersalone without the creation of additional anchoring structures has beendetermined not to create a sufficiently high population of anchoringstructures to meet the pull-off strength requirement of the metal-cladpolymer article.

Desired metallic material-polymeric material interface surface featurescan be generated in a shaped polymer precursor article or a metalliclayer in several ways:

1. Mechanical Surface Roughening of the Polymer and/or Metal Interface:

The surface of the substrate to be coated can be suitably roughened by amechanical process, e.g., by sanding, grid blasting, grinding and/ormachining.

2. Imprinting of the Polymer Surface by Molding and/or Other ShapingMethods:

Desirable anchoring structures can be imprinted/patterned on the surfaceof the substrate to be coated by suitable polymer molding, stamping,forming and/or shaping methods applying pressure to the soft, softenedor molten polymer surface, including but not limited to injection andcompression molding, and “print rolling” which transfer the desiredtexture to the polymer substrate surface.

3. Chemical Etching of the Polymer and/or Metal Interface Near-Surface:

Chemical etching using oxidizing chemicals such as mineral acids, basesand/or oxidizing compounds such as permanganates is the most popularmethod for etching polymers practiced in industry. This method alsobenefits from the use of “platable polymer grades” which contain fillermaterials which, in the near outer surface layer, are dissolved duringthe etching process.

The co-pending application by MeCrea entitled “Anodically AssistedChemical Etching of Conductive Polymers and Polymer Composites”discloses a surface activation process for conductive polymers/polymercomposites consisting of simultaneously applying anodic polarization andchemical etching, referred to as “anodically-assisted chemical-etching”or “anodic assisted etching”. This process drastically enhances the bondstrength between the activated substrate and the applied coating.Simultaneous chemical and electrochemical etching of polymericsubstrates substantially enhances the bond, peel and shear strengthbetween the polymeric substrate and the applied metallic coating/layeras highlighted in the co-pending application.

Solvent free chemical etching can be employed as well, to etch and/orsuitably texture the outer surface including plasma etching or etchingwith reactive gases including, but not limited to, SO₃ and O₃, tosuitably precondition and texture the surface.

4. Swelling of the Polymeric Substrate Surface:

Application of swelling agents to create anchoring structures in thenear surface of the polymer with or without the use of etching andabrasion methods can be employed. Suitable swelling agents includeorganic solvents for one or more polymers in the substrate.

5. Applying Adhesive Layers or Partially Cured Polymeric Substrates:

Where applicable, partly cured polymer substrates may be activated andcoated, followed by an optional curing heat treatment. Similarly,adhesive layers may be applied between the polymeric substrate and themetallic coating which can also be followed by an optional curing heat.

6. Post Cure Treatment of Metal-Clad Polymer Articles:

Another process that can be used to to improve the adhesion between thepolymeric substrate and the metallic layer entails a suitable heattreatment of the metal-clad article for between 5 minutes and 50 hoursat between 50 and 200° C.

7. Applying the Polymer to a Rough Metal Surface:

Another approach entails first forming the metallic layer with onesurface to be covered by the polymer purposely “roughened” andcontaining suitable surface features/protrusions/surface roughness tocreate anchoring structures elevating from the metallic surface,recessing into the metal surface or their combinations, to aid inenhancing the adhesion to the polymeric substrate. In this case thepolymeric material is applied onto the metallic material and notvice-versa.

Combinations of two or more of the aforementioned processes can be usedas well and the specific pretreatment conditions typically need to beoptimized for each polymer and molded part to maximize the bond strengthwhich can be conveniently determined using the pull off test described.

As highlighted, carbon-fiber and/or graphite-fiber and/or glass-fiber(referred to as carbon/graphite/glass-fiber) polymer composite molds arepopular for sporting goods, automotive and aerospace parts and forfabricating composite prototypes for the aerospace industry.Carbon/graphite/glass-fiber polymer composite molds are cheap but lackdurability and therefore find use only for prototyping. Depositing,e.g., fine-grained and/or amorphous metals such as Ni, Co, Cu and/orFe-based alloys onto the carbon/graphite-fiber polymer composite moldsprovides for tremendous cost savings over the traditional approach ofmachining and forming Invar molds.

Similarly, carbon/graphite-fiber polymer composites are also a popularchoice for aerospace components including plane fuselage, wings, rotors,propellers and their components as well as other external structuresthat are prone to erosion by the elements including wind, rain, hail andsnow or can be damaged with impact by debris, stones, birds and thelike. Aerospace and defense applications particularly benefit from astrong, tough, hard, erosion-resistant fine-grained and/or amorphouscoating. Lightweight laminate articles are also employed in internalairplane parts.

Suitable laminate metallic-material/polymeric-material articles include,but are not limited to, precision graphite fiber/epoxy molds used inaerospace, automotive and other industrial applications that are exposedto repeated temperature cycling (between −75° C. and up to 350° C.).Metal-clad polymer parts made from the fine-grained and/or amorphousmetallic coatings on appropriate substrates are well suited for highprecision molding components requiring great dimensional stability overa wide operating temperature range.

In applications where coatings are applied to substrates it is usuallydesired for the coefficient of linear thermal expansion (CLTE) of, e.g.,the metal coating to be closely matched to the CLTE of the polymericsubstrate or polymer composite to avoid delamination/failure duringthermal cycling. Similarly in molding applications (blow, injection,compression molding and the like) good matching of the thermal expansionproperties of all components is conventionally required to avoidspring-back and delamination during the heating and the cooling cycle.The tolerable “CLTE mismatch” between the metallic layer and the polymerdepends on the application, the quality of the adhesion between thecoating and the polymer substrate, the maximum and minimum operatingtemperature and the number of temperature cycles the article is requiredto withstand in its operating life. In all instances, after apredetermined number of thermal cycles, consisting either of submersingthe article in liquid nitrogen for one minute followed by submersion inhot water for one minute, or other suitable thermal cycling testsincluding ANSI/ASTM specification B604-75 section 5.4 Test (StandardRecommended Practice for Thermal Cycling Test for Evaluation ofElectroplated Plastics ASTM B553-71), the coating relative to theunderlying substrate should not fail. Delamination, blistering orcracking of the coating and/or the substrate which would compromise theappearance or performance of the article are all considered failure.Similarly, a displacement of the coating relative to the underlyingsubstrate of more than 2% constitutes failure.

Suitable permanent substrates include polymeric materials filled with orreinforced with e.g. graphite or glass which reduces the CLTE in atleast the plane of the polymeric substrate. For added strength,durability and high temperature performance filled polymers are verydesirable. The term “filled” as used herein refers to polymer resinswhich contain fillers embedded in the polymer, e.g., fibers made ofgraphite, carbon nanotubes, glass and metals; powdered mineral fillers(i.e., average particle size 0.2-20 microns) such as talc, calciumsilicate, silica, calcium carbonate, alumina, titanium oxide, ferrite,and mixed silicates. A large variety of filled polymers having a fillercontent of up to about 95% by weight are commercially available from avariety of sources. If required, e.g., in the case of electricallynon-conductive or poorly conductive substrates and the use ofelectroplating for the coating deposition, the substrates can bemetallized to render them sufficiently conductive for plating.

As highlighted, a number of processes can be used to form the metal-cladpolymer articles. In the case of using electroplating to apply themetallic layer to the polymer substrate, the polymer substrate, aftersuitably being appropriately shaped and activated, is preferablymetallized to enhance the surface conductivity typically by applying athin layer called the “intermediate conductive layer” or “metalizinglayer”. The intermediate conductive layer can comprise a metallic layeror can comprise polymeric material with conductive particulates therein.Where the intermediate conductive layer comprises a metallic layer, themetallic layer is constituted of Ag, Ni or Cu or a combination of anytwo or all of these, and the intermediate conductive layer can bedeposited by electroless deposition, sputtering, thermal spraying,chemical vapor deposition, physical vapor deposition of by any two ormore of these. Where the intermediate conductive layer comprisespolymeric material with conductive particulates therein, it can be, forexample, a conductive paint or a conductive epoxy. The conductiveparticulates can be composed of or contain Ag, Ni or Cu or graphite orother conductive carbon or a combination of two or more of these. Ashighlighted the surface of the metal layer or metal particulates can beoxidized to enhance adhesion.

The following working examples illustrate the benefits of the invention,specifically a comparison of pull-off and peel strength data for twosets of metal-clad polymer samples processed the same way, namely ABSpolymeric substrate coated with an organic adhesive layer that ispartially cured, then coated with a Ag intermediate layer and afine-grained Ni—Fe layer, followed by heat treatment to fully cure thepart (Working Example I); mechanically abraded graphite-fiber epoxysubstrates coated with fine-grained nickel (Working Example II);chemically and anodically etched carbon fiber cloth reinforcedbismaleimide substrates, then coated with a Ag intermediate layer andcoated with a fine-grained nickel-iron alloy (Working Example III);chemically etched graphite-fiber and glass fiber reinforced polymersubstrates coated with nickel-based materials with an amorphous orfine-grained microstructure using an intermediate conductive Ag layer(Working Example IV); coating of fully-cured and partially-curedgraphite reinforced polymer composites with a silver (Ag) intermediatelayer and a fine-grained Ni layer, including heat treatment of thepartially-cured coated part (Working Example V); coating of a chemicallyetched glass fiber reinforced polyamide polymer composite with a Ni—Pintermediate layer with a fine-grained Ni metal, followed by apost-plating heat-treatment (Working Example VI); and a polypropylenebacking layer applied to a fine-grained Co—P metal layer with a roughinterface surface produced electrochemically (Working Example VII).Intermediate metallizing layers were used in Working Examples I, III,IV, V and VI.

The invention is illustrated by the following working examples.

Working Example I Comparison of Pull-Off and Peel Strength for HighDensity ABS Substrate Coated with an Adhesive Layer, then Metallizedwith an Ag Intermediate Layer and a Fine-Grained Ni—Fe Layer with andwithout Heat Treatment of the Coated Part

Two 10×15 cm coupons were cut from a commercial 6 mm ABS sheet (CLTE:˜75×10⁻⁶ K⁻¹ in all directions) The coupons were ground on one side with80 grit SiC paper to a consistent surface roughness. The samples werethen cleaned with Alconox and steel wool, followed by ultrasonicallycleaning in deionized water for 5 minutes. The samples were rinsed inisopropanol, dried and degreased with 1,2-dichloroethane to remove anyresidual oils and/or films.

Subsequently, the coupons were coated on one side with a thin film of acommercial epoxy-based adhesive available from Henkel Canada, Brampton,Ontario (LePage 11). The epoxy based adhesive coating was then partiallycured at room temperature for 2 hours. Thereafter the panels werechemically etched at 65° C. for 5 minutes in alkaline permanganatesolution (M-Permanganate P, Product Code No. 79223) available fromMacDermid Inc. of Waterbury, Conn., USA. Following etching, the sampleswere rinsed in deionized water and submerged in neutralizer solution(M-Neutralize, Product Code No. 79225 also available from MacDermidInc.) for 5 minutes at room temperature. After neutralizing, the sampleswere rinsed with deionized water and metallized using a commercialsilvering solution (available from Peacock Laboratories Inc., ofPhiladelphia, Pa., USA; average grain size 28 nm) and coated with 20 μmof fine-grained Ni-58Fe (average grain size˜20 nm, CLTE: ˜2×10⁻⁶ K⁻¹)according to the process of U.S. Patent Publication No. U.S.2005-0205425 A1, published Sep. 22, 2005, the whole of which isincorporated herein by reference.

The metal clad articles had a yield strength of 44.6 MPa, an ultimatetensile strength of 47.3 MPa, a Young's modulus of 2.4 GPa and anelastic limit of 1.8%.

One of the panels was then subjected to a post-coating curing treatmentconsisting of heat treating the sample in a drying oven for anadditional 2 hours at 50° C. to fully cure the adhesive film. Pull-offand peel adhesion strength of the coatings on the two samples was thenmeasured following ASTM D4541-02 “Standard Test Method for Pull-OffStrength of Coatings Using Portable Adhesion Testers” using the“PosiTest AT Adhesion Tester” available from the DeFelsko Corporation ofOgdensburg, N.Y., USA and ASTM B533-85(2004) “Standard Test Method forPeel Strength of Metal Electroplated Plastics” using an Instron 3365testing machine equipped with the 90 degree peel test fixture, and a 5KNload cell, available from Instron Corporation, Norwood, Mass., USA. Inall cases debonding occurred between the polymer material surface andthe immediately adjacent metal layer.

The pull-off and peel adhesion strength for the two samples issummarized in the table below. While the pull-off strength was high andessentially the same for both samples, the sample that received apost-coating heat treatment to fully cure the adhesive film displayed amuch higher peel strength (more than three fold). This exampleillustrates that pull off tests and peel tests are not interchangeableand do not produce results which are comparable. Specifically to thisexample, as highlighted, pull-off strength exceeding 1,000 psi isconsidered “excellent” for structural metal-clad polymer parts. A peelstrength value of 4 N/cm Newton/cm), in the case of decorative metalcoatings on polymers, is considered to be “very poor”, whereas a peelstrength value of 12.5 N/cm is considered “excellent”.

TABLE 2 Pull-Off Strength Data (ASTM D4541-02) and Peel Strength Data(ASTM B533-85) for Samples With and Without Post Cure Heat Treatment.Pull-off Strength (ASTM Peel Strength (ASTM D4541-02) [psi] B533-85)[N/cm] Sample 1 without post- 1075 4.0 cure heat treatment Sample 2 withpost- 1100 12.5 cure heat treatment

Similar results were obtained when the intermediate layer comprised“electroless Ni”, available from various commercial vendors andconsisting of amorphous Ni—P, with a P content ranging from 2-15%,including Ni-7P available from MacDermid Inc., Waterbury, Conn., USA.

Working Example II Fine-Grained Ni Coated Graphite Reinforced CompositeActivated by Mechanical Abrasion

6 mm thick graphite fiber/epoxy sheets were sourced from NewportAdhesives and Composites, Irvine, Calif., USA, and were cut into 5 cm by5 cm coupons. The surface of the coupons was mechanically ground usingP1000 sandpaper exposing carbon fibers. The CLTE of the coupon in theplane was 5×10⁻⁶ K⁻¹ and normal to the plane 60×10⁶ K⁻¹. After surfacepreparation the surface roughness of the coupons was determined to beRa˜2.0 micron and Ry_(max)˜10.0 micron. Microscope analysis revealedthat the anchoring structures predominantly included cross-hatchedgrooves and their population amounted to about 1,000 per cm. The couponswere encapsulated to a coating thickness of ˜50 micron by depositingfine-grained Ni-20Fe alloys (average grain size˜20 nm, CLTE: ˜11×10⁻⁶K⁻¹) from a modified Watts nickel bath and using a Dynatronix (DynanetPDPR 20-30-100) pulse power supply as described in U.S. PatentPublication No. U.S. 2006-0135281-A1, published Jun. 22, 2006, the wholeof which is incorporated herein by reference.

The metal clad articles had a yield strength of 606 MPa, an ultimatetensile strength of 614 MPa, a Young's modulus of 71 GPa and an elasticlimit of 0.9%.

Coated samples were exposed to a thermal cycling test which involvesvertical submersion into liquid nitrogen (T=−196° C.) for one minute,immediately followed by submersion in hot water (T=90° C.) for oneminute. After ten cycles the sample is inspected for delamination,blistering, cracks and the like and the relative displacement of thecoating determined. Thirty such thermal cycles were performed. Allsamples passed the liquid nitrogen/hot water cycling test withoutdelamination. In addition, another set of samples was exposed to 10thermal cycles according to the ANSI/ASTM specification B604-75 section5.4 Thermal Cycling Test for Service Condition 4 (85° C. to −40° C.)without failure. Thereafter, the adhesion between the metallic layer andthe polymeric substrate was determined using ASTM D4541-02 Method Eusing the self alignment adhesion tester type V described in Annex A5,specifically the “PosiTest AT Adhesion Tester” available from theDeFelsko Corporation of Ogdensburg, N.Y., USA. The data are displayed inTable 3.

TABLE 3 Thermal Cycling/Adhesion Test Results ANSI/ASTM Pull-Off Thermalspecification Strength ASTM Min/ Coating Cycling Test B604-75 sectionD4541-02 Max Chemistry (~196/90° C.) 5.4 Thermal Method E Substrate(Average Coating Performance Cycling Test/ after 10 cycles CLTE GrainCLTE after 10 cycles/ SC4; 10 cycles/ of ASTM Substrate [10⁻⁶ Size [10⁻⁶Displacement Displacement B604-75/ Chemistry K⁻¹] in nm) K⁻¹]

 L/L [%]

 L/L [%] SC4 [psi] Graphite 5/60 80Ni 20Fe 11 Pass/~0 Pass/~0 350 Fiber/(15 nm) Epoxy Composite

Working Example III Fine-Grained Ni-58Fe Coated Carbon Fiber ClothReinforced Bismaleimide Polymer Composite Activated by Various Chemicaland Anodically Assisted Chemical Etching Methods, Use of a MetalizingLayer

3.75×8.75 cm coupons were cut from an 6 mm thick fully cured conductivecarbon-fiber reinforced plastic (CFRP) sheet of HTM 512, a bismaleimidepre-impregnated carbon fiber cloth composite used in high temperatureresistant composite tooling available from the Advanced Composites GroupLtd. of Heanor, Derbyshire, United Kingdom. The CLTE of the substratematerial is 3×10⁻⁶ K⁻¹ in the plane and 70×10⁻⁶ K⁻¹ in the directionnormal to the plane. The initial substrate preparation procedure was asfollows: (i) mechanically abrading all exposed surfaces using 320 gritto a uniform finish, (ii) scrubbing with steel wool and Alconox cleaner,followed by a rinse in deionized water and (iii) rinsing withisopropanol, followed by drying. Thereafter the composite coupons wereprocessed in various etching solutions, namely an alkaline permanganateetch, a chromic acid etch, a sulfuric acid etch and a sodium hydroxideetch with and without anodic assist. Microscope analysis revealedanchoring structures which included cross-hatched grooves, cavities,pined anchoring structures and protruding anchoring fibers and,depending on the sample, their population amounted to between about3,000 and about 25,000 per cm for the samples which passed the thermalcycling test. Subsequently, the samples were metallized using acommercial silvering solution (available from Peacock Laboratories Inc.,of Philadelphia, Pa., USA; average grain size 28 nm) and coated on oneside with a 50 μm thick layer of fine-grained Ni-58Fe (CLTE: ˜2×10⁻⁶K⁻¹, average grain size˜20 nm) according to US Patent Publication No. US2005-0205425 A1, published Sep. 22, 2005.

The metal clad articles had a yield strength of 604 MPa, an ultimatetensile strength of 608 MPa, a Young's modulus of 71 GPa and an elasticlimit of 0.9%.

Following plating, the adhesion strength was measured using ASTMD4541-02 Method E “Standard Test Method for Pull-Off Strength ofCoatings Using Portable Adhesion Testers” using the “PosiTest ATAdhesion Tester” made by DeFelsko Corporation of Ogdensburg, N.Y., USA.In all cases debonding occurred between the polymer material surface andthe adjacent metal layer. Samples were also exposed to 10 cyclesaccording to ANSI/ASTM specification B604-75 section 5.4, servicecondition 4.

For each different etch solution chemistry, CFRP samples were testedunder 3 different conditions: 1) passive dip in solution for 5 min, 2)anodically polarized at 50 mA/cm² for 5 min, and 3) anodically polarizedat 100 mA/cm² for 5 min. Following etching the samples were neutralized,as appropriate and then rinsed in deionized water and the resulting massloss from etching was documented.

The etch compositions, etching conditions, mass loss during etching andadhesion strength after etching are shown in the Tables 4-7 below. Inthis experiment only the permanganate etch under all conditions testedand the sulfuric acid control etch were found to result in a weightloss. The slight increase in mass in the other samples may be a resultof “swelling” (absorption of liquid) during etching which is known tooccur with various polymer substrates including fiber reinforced epoxycomposites.

In all etch solutions investigated a significant increase in adhesionstrength is obtained (>30%) by applying an anodic current assist duringetching without any increase in etching time. The adhesion strength wasfound to increase with increased anodic assisted etch current density(100 mA/cm² compared to 50 mA/cm²). The oxidizing etch solutions(permanganate and chromic) were found to provide the highest adhesionvalues.

All samples were also exposed to 10 cycles according to ANSI/ASTMspecification B604-75 section 5.4, service condition 4 and all samples,except for the sulfuric acid etch and NaOH etch for dipping only, passedthe test.

TABLE 4 Permanganate Etch Solution Type Chemical Composition MacDermidM-Permanganate: 60 g/L Permanganate Etch M-79224: 60 g/L 5 min @ 45° C.D.I. Water: 940 g/L Adhesion Thermal Cycling Test (ASTM D4541-(ANSI/ASTM B604-75 section 02 Method E) 5.4); Service Condition 4, 10Etching Type [psi] Cycles/Displacement

 L/L [%] Dip only 433 Pass/~0 Dip & Anodic 668 Pass/~0 Etch @ 50 mA/cm²Dip & Anodic 1069 Pass/~0 Etch @ 100 mA/cm²

TABLE 5 Sulfuric Acid Etch Solution Type Chemical Composition SulfuricAcid Etch H₂SO₄: 5% (in D.I. water) 5 min @ 25° C. Adhesion ThermalCycling Test (ASTM D4541- (ANSI/ASTM B604-75 section 02 Method E) 5.4);Service Condition 4, 10 Etching Type [psi] Cycles/Displacement

 L/L [%] Dip only 169 Failure/delamination Dip & Anodic 227 Pass/~0 Etch@ 50 mA/cm² Dip & Anodic 328 Pass/~0 Etch @ 100 mA/cm²

TABLE 6 Sodium Hydroxide Etch Solution Type Chemical Composition SodiumHydroxide NaOH: 25% (in D.I. water) Etch 5 min @ 25° C. Adhesion ThermalCycling Test (ASTM D4541- (ANSI/ASTM B604-75 section 02 Method E) 5.4);Service Condition 4, 10 Etching Type [psi] Cycles/Displacement

 L/L [%] Dip only 185 Failure/delamination Dip & Anodic 409 Pass/~0 Etch@ 50 mA/cm² Dip & Anodic 643 Pass/~0 Etch @ 100 mA/cm²

TABLE 7 Chromic Acid Etch Solution Type Chemical Composition ChromicAcid Etch 5 min @ 50° C. Chromic acid: 5% Phosphoric acid: 15% Sulfuricacid: 55% (in D.I. water) Adhesion Thermal Cycling Test (ASTM D4541-(ANSI/ASTM B604-75 section 02 Method E) 5.4); Service Condition 4, 10Etching Type [psi] Cycles/Displacement

 L/L [%] Dip only 408 Pass/~0 Dip & Anodic 772 Pass/~0 Etch @ 50 mA/cm²Dip & Anodic 893 Pass/~0 Etch @ 100 mA/cm²

Working Example IV Graphite or Glass-Filled Polymeric CompositesActivated by Acid Etching and Coated with an Amorphous Ni-Based MetallicLayer or Coated with an Intermediate Conductive Layer and a Fine-GrainedNi Layer

5 cm by 5 cm coupons (thickness 2 mm) of various substrates weresuitable pretreated using a chromic acid etch solution as per WorkingExample III Table 7 and coated with various fine-grained materialsavailable from Integran Technologies Inc. (www.integran.com; Toronto,Canada) to a metallic layer thickness of ˜100 micron. Substratematerials included graphite/epoxy sourced from Newport Adhesives andComposites, Irvine, Calif., USA and glass fiber/polyamide compositecoupons sourced from BASF, Florham Park, N.J., USA. After appropriatechemical activation (chromic acid etch according to Table 7, dip only)all samples subjected to electroplating were metallized using acommercial silvering solution (available from Peacock Laboratories Inc.,of Philadelphia, Pa., USA; average grain size 28 nm). Microscopeanalysis revealed anchoring structures that included cross-hatchedgrooves, cavities, pitted anchoring structures and protruding anchoringfibers and, depending on the sample, their population amounted tobetween about 3,000 and about 10,000 per cm. Subsequently, fine-grainedNi-based metallic layers were deposited from a modified Watts bath asdescribed in U.S. Patent Publication No. US 2005-0205425 A1, publishedSep. 22, 2005. Amorphous Ni-based layers (˜20 micron thick Ni-7P) weredeposited directly onto the etched polymeric substrates using anelectroless nickel bath available from MacDermid Inc., Waterbury, Conn.,USA.

Table 8 summarizes the mechanical properties of the metal clad polymerarticles.

TABLE 8 Mechanical Properties of the metal clad polymer articles. YieldUltimate Young's Substrate (2 mm Coating Chemistry Strength TensileModulus Elastic thick) (20 micron thick) [MPa] Strength [MPa] [GPa]Limit [%] Glass Ni—7P (amorphous) 146 146 6.6 2.2 Fiber/PolyamideWithout Ag Composite metalizing layer Glass Ni (15 nm) 148 152 7.4 2.0Fiber/Polyamide With Ag metalizing Composite layer Glass 50Ni—50Fe (20nm) 150 154 7.0 2.1 Fiber/Polyamide With Ag metalizing Composite layerGraphite Ni—7P (amorphous) 601 601 70 0.9 Fiber/Epoxy Without AgComposite metalizing layer Graphite Ni (15 nm) 603 608 71 0.9Fiber/Epoxy With Ag metalizing Composite layer Graphite 50Ni—50Fe (20nm) 605 610 70 0.9 Fiber/Epoxy With Ag metalizing Composite layer

The coated samples were exposed to the thermal cycling test describedabove. The adhesion strength was measured using ASTM D4541-02 Method Eusing the “PosiTest AT Adhesion Tester” available from the DeFelskoCorporation of Ogdensburg, N.Y., USA. In all cases debonding occurredbetween the polymer material surface and the immediately adjacent metallayer. The data displayed in Table 9 indicate that acceptable thermalcycling performance is achieved. All samples were also exposed to 10cycles according to ANSI/ASTM specification B604-75 section 5.4, servicecondition 4 without failure.

TABLE 9 Thermal Cycling/Adhesion Test Results Thermal Cycling TestPull-Off (−196 to 90° C.) Strength Min/Max Coating Coating PerformanceASTM Substrate Chemistry CLTE after 10 cycles/ D4541-02 Substrate CLTE(Average grain size [10⁻⁶ Displacement Method E Chemistry [10⁻⁶ K⁻¹] innm) K⁻¹]

 L/L [%] [psi] Glass 20/110 Ni—7P (amorphous) 20 Pass/~0 300Fiber/Polyamide Without Ag Composite metalizing layer Glass 20/110 Ni(15 nm) 13 Pass/~0 300 Fiber/Polyamide With Ag metalizing Compositelayer Glass 20/110 50Ni—50Fe (20 nm) 10 Pass/~0 300 Fiber/Polyamide WithAg metalizing Composite layer Graphite 5/55 Ni—7P (amorphous) 20 Pass/~0620 Fiber/Epoxy Without Ag Composite metalizing layer Graphite 5/55 Ni(15 nm) 13 Pass/~0 620 Fiber/Epoxy With Ag metalizing Composite layerGraphite 5/55 50Ni—50Fe (20 nm) 10 Pass/~0 620 Fiber/Epoxy With Agmetalizing Composite layer

Working Example V Coating of Fully-Cured and Partially-Cured GraphiteReinforced Polymer Composites with a Silver (Ag) Intermediate Layer anda Fine-Grained Ni—Fe Layer, Including Heat-Treatment of thePartially-Cured Coated Part

Three 15×15 cm samples of 6 mm thick conductive carbon-fiber reinforcedplastic (CFRP) sheet (CLTE: in the plane 3×10⁻⁶ K⁻¹ and CLTE: ˜60×10⁻⁶K⁻¹ normal to the plane) were obtained from Janicki Industries ofSedro-Wooley, Wash., USA. Two of the panels were only “partially” cured,while the third panel was “fully” cured. The coupons were ground on oneside with 80 grit SiC paper to a consistent surface roughness, cleanedwith Alconox and steel wool, followed by ultrasonically cleaning indeionized water for 5 minutes. The samples was then rinsed inisopropanol, dried and degreased with 1,2-dichloroethane to remove anyresidual oils and/or films.

The CFRP panels were then chemically etched in a standard acidsulfo-chromic etch solution consisting of 300 g/L chromic acid and 250g/l sulfuric acid in deionized water. After surface preparation thesurface roughness of the coupons was determined to be Ra˜2.0 micron andRy_(max)˜10.0 micron. Microscope analysis revealed that the anchoringstructures included cavities and pitted anchoring structures and theirpopulation ranged from about 1,000 to about 25,000 per cm. Followingetching, the samples were rinsed in deionized water and submerged inneutralizer solution consisting of 5 g/l of sodium metabisulfite for 5minutes at room temperature. After neutralizing, the samples were rinsedwith deionized water and metallized using a commercial silveringsolution (available from Peacock Laboratories Inc., of Philadelphia,Pa., USA; average grain size 28 nm) and coated with 50 μm offine-grained Ni (average grain size˜15 nm, CLTE: ˜13×10⁻⁶ K⁻¹) accordingto the process of US Patent Publication No. US 2005-0205425 A1,published Sep. 22, 2005.

The metal clad articles had a yield strength of 602 MPa, an ultimatetensile strength of 606 MPa, a Young's modulus of 7.4 GPa and an elasticlimit of 0.9%.

One of the panels was then subjected to a post-coating heat-treatment ina drying oven for an additional 2 hours at 177° C. to fully cure thepartially cured panel. The pull-off adhesion strength of the coatings ofthe three CFRP samples was then measured following ASTM D4541-02“Standard Test Method for Pull-Off Strength of Coatings Using PortableAdhesion Testers” using the “PosiTest AT Adhesion Tester” available fromthe DeFelsko Corporation of Ogdensburg, N.Y., USA.

The pull-off adhesion strength for the three samples is summarized inthe Table 10. The pull-off strength for the “partially” cured sample wasfound to be significantly higher than that of the “fully” cured sample.The data also shows that a further increase in adhesion strength can beobtained by fully curing the “partially” cured CFRP panel after themetal coating. All samples were also exposed to 10 cycles according toANSI/ASTM specification B604-75 section 5.4, service condition 4 withoutfailure.

TABLE 10 Pull-Off Strength Data (ASTM D4541-02) for Samples. Pull-offThermal Cycling Test Strength (ANSI/ASTM B604-75 (ASTM section 5.4);Service D4541-02) Condition 4, 10 Cycles/ [psi] Displacement

 L/L [%] Coated of fully cured 490 Pass/~0 CFRP-substrate Coated ofpartially cured 1542 Pass/~0 CFRP-substrate Coated of partially cured2078 Pass/~0 CFRP-substrate with post-plate heat treatment (2 hours at177° C.)

Working Example VI Glass-Filled Polymer Composites Activated by AcidEtching and Coated with an Amorphous Ni-Based Intermediate ConductiveLayer and a Fine-Grained Ni Layer, Followed by Post Plate Heat-Treatment

5 cm by 5 cm coupons (thickness 2 mm) were cut from a commerciallyavailable 14% glass-filled polyamide substrate (Caspron®, BASF, FlorhamPark, N.J., USA.). The CLTE of the coupon in the plane was 32×10⁻⁶ K⁻¹and normal to the plane 70×10⁻⁶ K⁻¹. Samples were suitable pretreatedusing a chromic acid etch solution as per Working Example III Table 7(dip only). After neutralizing, the samples were rinsed with deionizedwater and metallized using a commercial amorphous electroless Ni-7Pcoating available from MacDermid Inc. of Waterbury, Conn., USA andthereafter coated with 20 μm thick fine-grained nickel (average grainsize 20 nm, CTE 13×10⁻⁶ K⁻¹) according to the process of US PatentPublication No. US 2005-0205425 A1, published Sep. 22, 2005, availablefrom Integran Technologies Inc. (www.integran.com; Toronto, Canada).

The metal clad articles had a yield strength of 148 MPa, an ultimatetensile strength of 152 MPa, a Young's modulus of 7.4 GPa and an elasticlimit of 2.0%.

Microscope analysis revealed that anchoring structures includedcross-hatched grooves, cavities, pitted anchoring structures andprotruding anchoring fibers and amounted to between about 10,000 and15,000 per cm. Selected samples were heat treated at 80° C. and theadhesion and thermal cycling performance determined. The peel andpull-off adhesion strength of the samples was then measured followingASTM D4541-02 “Standard Test Method for Pull-Off Strength of CoatingsUsing Portable Adhesion Testers” and ASTM B533-85(2004) “Standard TestMethod for Peel Strength of Metal Electroplated Plastics” using anInstron 3365 testing machine equipped with the 90 degree peel testfixture, and a 5KN load cell, available from Instron Corporation,Norwood, Mass., USA. In all cases debonding occurred between the polymermaterial surface and the immediately adjacent metal layer. The datadisplayed in Table 11 indicate that acceptable thermal cyclingperformance is achieved. All samples were also exposed to 10 cyclesaccording to ANSI/ASTM specification B604-75 section 5.4, servicecondition 4 without failure. It is noted that post-platingheat-treatment modestly enhances the pull-off strength whereas the peelstrength drastically deteriorates. As highlighted above and illustratedin Example 1 there is no correlation between pull-off and peel strengthdata.

TABLE 11 Thermal Cycling/Adhesion Test Results Post Pull-Off ThermalCycling Test Coating Plating Strength Peel (ANSI/ASTM B604-75 Min/MaxChemistry Heat- ASTM Strength section 5.4); Service Substrate (AverageCoating Treatment D4541-02 (ASTM Condition 4, 10 CLTE grain size CLTEDuration at Method E B533-85) Cycles/Displacement [10⁻⁶ K⁻¹] in nm)[10⁻⁶ K⁻¹] 80° C. [hrs] [psi] [N/cm]

 L/L [%] 32/70 Ni (15 nm) 13 0 862 9 Pass/~0 With NiP metalizing layer32/70 Ni (15 nm) 13 1 932 7 Pass/~0 With NiP metalizing layer 32/70 Ni(15 nm) 13 2 885 5 Pass/~0 With NiP metalizing layer

Working Example VII Fine-Grained Co—P Metal Layer with a Rough SurfaceProduced Electrochemically Prior to Applying a Polymer Based BackingLayer

A metal-clad polymer part was fabricated from two components, namely aface plate comprised of a durable electroformed fine-grained Co-2P alloy(15 nm average grain size, CLTE in plane and normal to it: ˜15×10⁻⁶K⁻¹), and a polymer backing structure comprising a thermoplastic polymer(polypropylene, CLTE in plane and normal to it: 85×10⁻⁶ K⁻¹). Ratherthan coating the activated polymer substrate with a fine-grained metal,the layers were applied in reverse order, namely the first step entailedplating the fine-grained Co-2P alloy layer (average grain size 15 nm)according to US Patent Publication No. US 2005-0205425 A1, publishedSep. 22, 2005, onto a polished temporary titanium substrate. Afterbuilding up the fine-grained metallic layer to a thickness ofapproximately 250 microns, the applied current density was raisedsubstantially to deposit a rough “bonding surface” with anchoringstructures including protrusions and dendritic nodules with a poroussubstructure and, depending on the sample, their population count rangedbetween about 100 and about 3,000 per cm. After plating, the surfaceroughness of the metallic layer, to serve as interface with thepolymeric layer, was determined to be Ra˜125 micron and Ry_(max)˜250micron. As outlined, the important feature of the design is to purposelycreate a rough surface on the backside of the faceplate which allows forexcellent adhesion between the metal faceplate and the polymer backingstructure. A polypropylene substrate backing was applied to the roughside of the fine-grained metal layer in a subsequent step by compressionmolding to an ultimate thickness of 6 mm. Metal-clad polymer samplesexposed to 10 cycles according ANSI/ASTM specification B604-75 section5.4, service condition 4, did not fail and the adhesion strength valuesthat have been obtained using ASTM D4541-02 Method E all exceeded 300psi. The metal clad articles had a yield strength of 96 MPa, an ultimatetensile strength of 113 MPa, a Young's modulus of 6.5 GPa and an elasticlimit of 1.0%.

Variations

The foregoing description of the invention has been presented describingcertain operable and preferred embodiments. It is not intended that theinvention should be so limited since variations and modificationsthereof will be obvious to those skilled in the art, all of which arewithin the spirit and scope of the invention.

1. A metal-clad polymer article comprising: (i) a polymeric materialwhich at room temperature has a coefficient of linear thermal expansionin the range between 30×10⁻⁶ K⁻¹ and 250×10⁻⁶ K⁻¹ in at least onedirection; (ii) a metallic material having a microstructure which isfine-grained with an average grain size between 2 and 5,000 nm and/or anamorphous microstructure, wherein said metallic material consistsessentially of pure nickel or comprises a nickel alloy, said metallicmaterial forming a metallic material layer having a thickness between 10microns and 500 microns and said metallic material having a coefficientof linear thermal expansion at room temperature in all directions in therange between −5.0×10⁻⁶ K⁻¹ and 25×10⁻⁶ K⁻¹; (iii) at least oneintermediate layer between the polymeric material and the metallicmaterial layer, said at least one intermediate layer includes a metalliclayer consisting essentially of pure nickel or comprises a nickel alloy;(iv) an interface formed between the polymeric material and the at leastone intermediate layer and an interface formed between the at least oneintermediate layer and the metallic material layer; and (v) an anchoringstructure at least at said interface between the polymeric material andthe at least one intermediate layer comprising recesses and/orprotrusions to increase the interface area and provide enhanced physicalbond at the interface between the polymeric material and the at leastone intermediate layer, (vi) wherein said metal-clad polymer articleexhibits a pull-off strength between the polymeric material and themetallic material layer exceeding 200 psi as determined by ASTM D4541-02Method A-E.
 2. The article of claim 1, wherein the interface formedbetween the at least one intermediate layer and the metallic materiallayer also includes an anchoring structure comprising recesses and/orprotrusions to increase the interface area and provide enhanced physicalbond at the interface between the at least one intermediate layer andthe metallic material layer.
 3. The article according to claim 1 whereinthe surface roughness of the polymeric material and/or the metallicmaterial layer at their interface is in the range of Ra=0.01 micron andRa=500 micron and/or Ry=0.02 micron and Ry=5,000 micron and/orRy_(max)=0.02 micron and Ry_(max)=5,000 micron and/or Rz=0.02 micron andRz=5,000 micron.
 4. The article according to claim 1, wherein saidmetallic material layer comprises a nickel alloy, said nickel alloy ofsaid metallic material layer is an alloy with a material selected fromthe group consisting of: one or more metals selected from the groupconsisting of Ag, Al, Au, Co, Cr, Cu, Fe, Mo, Pd, Pt, Rh, Ru, Sn, Ti, W,Zn and Zr; wherein said metallic material layer optionally includes atleast one element selected from the group of B, C, H, O, P and S; andoptionally further includes particulate additions.
 5. The articleaccording to claim 1, wherein when said metallic material layercomprises a nickel alloy, and wherein the metallic material layerfurther comprises particulate addition and said particulate additioncomprises at least one material selected from the group consisting of ametal selected from the group consisting of Ag, Al, Cu, In, Mg, Si, Sn,Pt, Ti, V, W, and Zn; a metal oxide selected from the group consistingof Ag₂O, Al₂O₃, SiO₂, SnO₂, TiO₂, and ZnO; a carbide of B, Cr, Bi, Si,and W; carbon selected from the group consisting of carbon nanotubes,diamond, graphite, and graphite fibers; ceramic; glass; and polymermaterial selected from the group consisting of PTFE, PVC, PE, PP, ABS,and epoxy resin.
 6. The article according to claim 1, wherein saidpolymeric material is a thermoplastic polymer.
 7. The article accordingto claim 1, wherein the metallic material layer represents between 5 and95% of the total weight of the article.
 8. The article according to ofclaim 1, wherein said article is a component or part of an automotive,aerospace, sporting equipment, manufacturing or industry application. 9.The article according to claim 8, said article is selected from thegroup consisting of cylindrical objects, medical equipment, componentsand housings for electronic equipment, automotive components, industrialproducts, molds and molding tools, aerospace parts, and militaryproducts.
 10. The article according to claim 1, wherein said article hasa tubular structure and said fine-grained metallic material layerextends over at least part of the inner or outer surface of said tubularstructure.
 11. The article according to claim 10 selected from the groupof gun barrels, drive shafts, arrow shafts, golf shafts, tubes, pipes,rods, fishing rods, cartridge casing, baseball bats, softball bats,hockey sticks, wires, cables, and fishing, skiing and hiking poles. 12.The article according to claim 9, wherein said article comprises apolymeric substrate containing glass fibers and/or at least onecarbon-containing material selected from the group consisting ofgraphite, graphite fibers, carbon, carbon fibers and carbon nanotubes.13. The article of claim 1 where the metallic material layer has athickness between 50 and 500 microns.
 14. The article of claim 1,wherein said at least one intermediate layer is an electricallyconductive or an adhesive layer.
 15. The article of claim 1, wherein theanchoring structure comprises at least one shape selected from the groupconsisting of ink bottle shaped cavities, pitted anchoring structures,anchoring surfaces with protruding anchoring fibers, grooved, roughenedanchoring surface structures, etched anchoring surface structures,dimples and mounds.
 16. The article of claim 15, wherein the anchoringstructure at the interface between the polymeric material and the atleast one intermediate layer and/or the interface between the at leastone intermediate layer and the metallic material layer has topographywhich has a population of recesses and/or protrusions to enhance thephysical bond to the metallic material layer in the range of 1 to10,000,000 per mm² of interface(s) area, said recesses and/or protrusionhaving a height/depth range between 10 nm and 1 mm and a diameterranging between 50 nm and 1 mm.
 17. The article of claim 1, wherein adisplacement of said metallic material layer relative to the polymericmaterial after at least one temperature cycle according to ASTM B553-71service condition 1, 2 3 or 4 is less than 2%.
 18. The article of claim1, wherein the coefficient of linear thermal expansion at roomtemperature in all directions of the metallic material layer is at least20% less than the coefficient of linear thermal expansion at roomtemperature in at least one direction of the polymeric material.
 19. Thearticle according to claim 8, wherein the article is a component orhousing for equipment selected from the group consisting of laptops,cell phones, personal digital assistant devices, MP3 players, cameras,image recording devices, and TVs.
 20. The article according claim 8,wherein the article is an aerospace part selected from the groupconsisting of a wing, wing part, wing flap, wing access cover,structural spar, rib, propeller, rotor, rotor blade, rudder, cover,housing, fuselage part, nose cone, landing gear, lightweight cabin part,cryogenic storage tank, duct, and interior panels.
 21. The articleaccording to claim 1, wherein said metal-clad polymer article orportions therefore have a yield strength and/or ultimate tensilestrength of between 10 and 7,500 MPa and an elastic limit between 0.5and 30%.
 22. The article according to claim 1, wherein said metal-cladpolymer article exhibits no delamination after said article has beenexposed to at least one temperature cycle according to ASTM B553-71service condition 1, 2, 3 or
 4. 23. A method for preparing a metal-cladpolymer article of claim 1 comprising the steps: (i) providing thepolymeric material which at room temperature has a coefficient of linearthermal expansion in the range between 30×10⁻⁶ K⁻¹ and 250×10⁻⁶K⁻¹ in atleast one direction, (ii) providing the metallic material having amicrostructure which is fine-grained with an average grain size between2 and 5,000 nm and/or an amorphous microstructure, wherein the metallicmaterial consists essentially of pure nickel or comprises a nickelalloy, and said metallic material is in the form of a metallic materiallayer having a thickness between 10 microns and 500 pm and a coefficientof linear thermal expansion at room temperature in all directions in therange between −5.0×10⁻⁶ and 25×10⁻⁶ K⁻¹, (iii) providing the at leastone intermediate layer, said at least one intermediate metallic layerincludes a layer consisting essentially of pure nickel or comprises anickel alloy, (iv) providing the interface between the polymericmaterial and the at least one intermediate layer and between the atleast one intermediate layer and the metallic material layer, and (v)providing the anchoring structure at least at said polymeric materialinterface.
 24. The method of claim 23 where the coefficient of linearthermal expansion at room temperature in all directions of the metallicmaterial layer and the at least one intermediate layer being at least20% less than the coefficient of linear thermal expansion in at leastone direction of the polymeric material.
 25. The method of claim 23,wherein the metallic material layer is deposited onto the polymericsubstrate having the at least one intermediate layer having anchoringstructure associated therewith by electrodeposition.
 26. The method ofclaim 23, wherein the polymeric material is applied to the metallicmaterial layer having the at least one intermediate layer havinganchoring structure associated therewith.